Flexible OLED display panel and manufacturing method thereof

ABSTRACT

The present invention provides a flexible organic light-emitting diode (OLED) display panel, which includes a first polyimide layer, a barrier layer and a second polyimide layer that are sequentially stacked and a thin film transistor (TFT) structure and an OLED structure that are sequentially disposed on the second polyimide layer, in which a material of the barrier layer includes at least one of silicon dioxide and silicon nitride. By arranging a flexible base as an upper polyimide layer and a lower polyimide layer and adding a barrier layer between the two polyimide layers, the present invention can effectively block water and oxygen from entering an interior of a component through a flexible polyimide base, thereby protecting the TFT structure and the OLED structure and improving the lifespan of the OLED display panel. The present invention further provides a manufacturing method of a flexible OLED display panel.

RELATED APPLICATIONS

The present application is a National Phase of International ApplicationNumber PCT/CN2017/112893, filed Nov. 24, 2017, and claims the priorityof China Application No. 201711039262.9, filed Oct. 30, 2017.

FIELD OF THE DISCLOSURE

The present invention relates to the field of display panel technology,and more particularly to a flexible organic light-emitting diode (OLED)display panel and a manufacturing method thereof.

BACKGROUND

With the development of the display technology, people increasinglydemand higher and higher quality of color and lightness, flexibleorganic light-emitting diode (OLED) displays are now gradually enteringinto consumer electronics markets of mobile devices, televisions, etc.As a flexible display, a polyimide layer manufactured mainly frompolyimide (PI) is a flexible substrate of thin film transistor (TFT)structures and OLED structures. However, the polyimide layer has poorability of blocking oxygen (O₂) and water (H₂O), which would result inan amount of water or oxygen penetrating through the polyimide layerinto circuits of the TFT structure and thus affect the lifespan of theOLED luminescent material.

Thus, it is desired to provide a flexible OLED display panel, which canwell block water and oxygen from entering into the TFT structure throughthe flexible base and can prolong the lifespan of the OLED luminescentmaterial.

SUMMARY

On this account, the present invention provides a flexible organiclight-emitting diode (OLED) display panel, which can effectively blockwater and oxygen from penetrating through a flexible polyimide base forprotecting thin film transistor (TFT) structures and OLED structures andimproving the luminescent lifespan of the OLED display panel.

First, the present invention provides a flexible OLED display panel,which includes sequentially stacked first polyimide layer, barrierlayer, second polyimide layer, and a TFT structure and an OLED structurewhich are sequentially disposed on the second polyimide layer, and amaterial of the barrier layer that includes at least one of silicondioxide and silicon nitride.

In one embodiment, the barrier layer includes a single-layered silicondioxide layer or a single-layered silicon nitride layer, or alternatelystacked silicon dioxide layers and silicon nitride layers.

In one embodiment, a thickness of the barrier layer is 0.1-2.0 μm.

In one embodiment, an oxygen barrier layer is further disposed betweenthe second polyimide layer and the TFT structure, and a material theoxygen barrier layer includes at least one of silicon dioxide andsilicon nitride. A thickness of the oxygen barrier layer is 0.1-1.5 μm.

In one embodiment, an organic film is further disposed between the TFTstructure and the OLED structure, and the organic film simultaneouslycovers a side edge of the TFT structure that is near a terminal of anon-display panel and partially covers the second polyimide layer, and amaterial of the organic film includes one or more of polyethylene,polypropylene, polystyrene, polylactic acid, polyethylene terephthalate,polyimide and polyester. A thickness of the organic film is 0.5-20 μm.

In one embodiment, a material of each of the first polyimide layer andthe second polyimide layer is polyimide resin or modified polyimideresin.

In one embodiment, a thickness of each of the first polyimide layer andthe second polyimide layer is 3-20 μm.

According to a first aspect, an embodiment of the present inventionprovides a flexible OLED display panel, which can effectively blockwater and oxygen from entering an interior of a component through aflexible polyimide base by arranging a flexible base as an upperpolyimide layer and a lower polyimide layer and adding a barrier layerbetween the two polyimide layers, thereby protecting the TFT structureand the OLED structure and improving the lifespan of the OLED displaypanel.

Second, the present invention provides a manufacturing method of aflexible OLED display panel, which includes the following steps:

providing a rigid substrate;

sequentially manufacturing a first polyimide layer, a barrier layer, asecond polyimide layer, a TFT structure and an OLED structure on therigid substrate; wherein a the barrier layer includes at least one ofsilicon dioxide and silicon nitride;

applying a laser lift-off process to separate the rigid substrate andthe first polyimide layer, so as to obtain a flexible OLED displaypanel.

In one embodiment, the barrier layer includes a single-layered silicondioxide layer or a single-layered silicon nitride layer, or includesalternately stacked silicon dioxide layers and silicon nitride layers, athickness of the barrier layer is 0.1-2.0 μm.

In one embodiment, a material of the first polyimide layer and thesecond polyimide layer is polyimide resin or modified polyimide resin. Athickness of each of the first polyimide layer and the second polyimidelayer are 3-20 μm.

In one embodiment, the manufacturing method further includesmanufacturing an oxygen barrier layer between the second polyimide layerand the TFT structure, and/or manufacturing an organic film between theTFT structure and the OLED structure, wherein a material of the oxygenbarrier layer includes at least one of silicon dioxide and siliconnitride, and the organic film simultaneously covers a side edge of theTFT structure that is near to a terminal of a non-display area andpartially covers the second polyimide layer, and a material of theorganic film includes one or more of polyethylene, polypropylene,polystyrene, polylactic acid, polyethylene terephthalate and polyester.

In one embodiment, the rigid substrate includes a glass substrate, awafer, a metal thin film or a rigid thin film.

According to a second aspect, an embodiment of the present inventionprovides a manufacturing method of a flexible OLED display panel, inwhich a composite flexible base with a first polyimide layer/a barrierlayer/a second polyimide layer is obtained and can well block water andoxygen from entering into the TFT structure or the OLED structure andprolong the luminescent lifespan of the OLED display panel, so as toimprove the product manufacturing quality.

The following specification partially describes advantages of thepresent invention, where some of these advantages are apparent accordingto this specification, or can be learned by practicing the embodimentsof the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural schematic diagram of a flexible OLED displaypanel that includes a single-layered structure of a barrier layerprovided by an embodiment of the invention.

FIG. 2 is a structural schematic diagram of a flexible OLED displaypanel that includes a multi-layered structure of a barrier layer of aflexible OLED display panel provided by an embodiment of the invention.

FIG. 3 is a structural schematic diagram of a flexible OLED displaypanel provided by an embodiment of the invention.

FIG. 4 is a structural schematic diagram of a flexible OLED displaypanel provided by an embodiment of the invention.

FIG. 5 is a structural schematic diagram of a flexible OLED displaypanel provided by an embodiment of the invention

FIG. 6 is a flowchart of a manufacturing process of a flexible OLEDdisplay panel provided by an embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following description is only the preferred examples of the presentinvention, and it should be pointed out that, the ordinary personskilled in the art can make various improvements and modificationswithout departing from the principle of the present invention, and theseimprovements and modifications should all fall into the protection scopeof the present invention.

As shown in FIG. 1, the present invention provides a flexible OLEDdisplay panel 100, which includes a first polyimide layer 10, a barrierlayer 20 and a second polyimide layer 30 that are sequentially stacked,and a thin film transistor (TFT) structure 40 and an organiclight-emitting diode (OLED) structure (not shown in FIG. 1) that aresequentially disposed on the second polyimide layer 30, and a materialof the barrier layer includes at least one of silicon dioxide andsilicon nitride.

In one embodiment of the present invention, the barrier layer 20 isdisposed between the first polyimide layer 10 and the second polyimidelayer 30, and the first polyimide layer 10, the barrier layer 20 and thesecond polyimide layer 30 tightly adhere together; the barrier layer 20may be manufactured from a silicon dioxide (SiO₂) material, a siliconnitride (SiN_(x)) material or a composite material of SiO₂ and SiN_(x);a thickness of the barrier layer 20 is 0.1-2.0 μm, and particularly, maybe 0.2 μm, 0.8 μm, 1 μm or 1.5 μm.

In an embodiment of the present invention, the barrier layer includes asingle-layered silicon dioxide layer.

In another embodiment of the present invention, the barrier layerincludes a single-layered silicon nitride layer.

In another embodiment of the present invention, the barrier layerincludes alternately stacked silicon dioxide layers and silicon nitridelayers. The arrangement of the silicon dioxide layers and the siliconnitride layers interior of the barrier layer 20 may be written asA-B-A-B-A-B- . . . , i.e., (AB)n, in which n is an integer greater thanor equal to 1, and A represents an silicon dioxide layer, and Brepresents a silicon nitride layer. The multi-layered structure of thebarrier layer 20 may lengthen penetrating paths of water and oxygen andtherefore includes more outstanding steam and oxygen blocking ability.As shown in FIG. 2, the barrier layer 20 provided by an embodiment ofthe invention may further include a first SiO₂ layer 201, and a SiN_(x)layer 202 and a second SiO₂ layer 203 that are alternating stacked, anda thickness of the first SiO₂ layer 201 is 0.1-2.0 μm, and a thicknessof the SiN_(x) layer 202 is 0.1-2.0 μm, and a thickness of the secondSiO₂ layer 203 is 0.1-2.0 μm.

In one embodiment of the present invention, in comparison with a singlepolyimide flexile base or another flexible base made from an organicpolymeric material, the composite base structure consisting of the firstpolyimide layer 10, the barrier layer 20 and the second polyimide layer30 has the following characteristics: on one hand, the composite basestructure consisting of the first polyimide layer 10, the barrier layer20 and the second polyimide layer 30 has good water and oxygen blockingfunction and thus greatly reduces the possibility of water and oxygenpenetrating through the flexible base, so as to protect the TFTstructure and the OLED structure and prolong the lifespan of the OLEDdisplay panel; on the other hand, the composite flexible base structurealso has good flexibility and thus can be widely applied formanufacturing a flexible panel.

A material of the first polyimide layer 10 and the second polyimidelayer 30 provided by an embodiment of the present invention is polyimideresin or modified polyimide resin. A thickness range of the firstpolyimide layer 10 is 3-20 μm, and a thickness range of the secondpolyimide layer 30 is 3-20 μm; a thicknesses of the first polyimidelayer 10 and the second polyimide layer 30 may be different, and thespecific thickness thereof may be selected in accordance with practicalcomponent types.

In one embodiment of the present invention, the TFT structure 40includes a buffer layer 41, a first gate insulating layer (GI1) 42, asecond gate insulating layer (GI2) 43 and a dielectric layer 44 that arestacked and functional components distributed therein, in which thefunctional components include a polysilicon layer 45, a first gateelectrode (GE1) 46, a second gate electrode (GE2) 48, a first drainelectrode 47 and a second drain electrode 49. In one embodiment, thepolysilicon layer 45 is arranged in the interior of the first gateinsulating layer 42 and adheres near to the lower surface of the firstgate insulating layer 42 and to the buffer layer 41; the first gateelectrode 46 is arranged in the second gate insulating layer 43; thesecond gate electrode 48 is arranged in the dielectric layer 44; thefirst drain electrode 47 and the second drain electrode 49 penetratesequentially through the dielectric layer 44 and the second gateinsulating layer 43 and connect with the polysilicon layer 45; the firstgate electrode 46 and the second gate electrode 48 are arranged betweenthe first drain electrode 47 and the second drain electrode 49. The TFTstructure 400 is a normal technical structure, and the present inventiondoes not make particular limitations.

Another embodiment of the present invention provides a flexible OLEDdisplay panel 300, which includes, as shown in FIG. 3, a first polyimidelayer 310, a barrier layer 320 and a second polyimide layer 330 that aresequentially stacked and an oxygen barrier layer 350, a TFT structure340 and an OLED structure (not shown in FIG. 3) that are sequentiallydisposed on the second polyimide layer 330; the oxygen barrier layer 350is disposed between the second polyimide layer 330 and the TFT structure340 and adheres together with a buffer layer 341 of the TFT structure340; a material of the oxygen barrier layer 350 includes at least one ofsilicon dioxide and silicon nitride. A thickness of the oxygen barrierlayer 350 is 0.1-1.5 μm. The oxygen barrier layer 350 can further blockwater and oxygen that penetrate through the substrate, in order toprotect the TFT structure and prolong the luminescent lifetime of thedisplay panel.

Another embodiment of the present invention provides a flexible OLEDdisplay panel 400, which includes, as shown in FIG. 4, a first polyimidelayer 410, a barrier layer 420 and a second polyimide layer 430 that aresequentially stacked and a TFT structure 440, an organic film 450 and anOLED structure (not shown in FIG. 4) that are sequentially disposed onthe second polyimide layer 430; the organic film 450 is disposed betweenthe TFT structure 440 and the OLED structure, and the organic film 450simultaneously covers a side edge of the TFT structure 440 that is neara terminal of a non-display area and partially covers the secondpolyimide layer 430. The organic film 450 is stacked on the dielectriclayer 441, and simultaneously the organic film 450 and the TFT structure440 are all stacked on second polyimide layer 430. In addition, theorganic film 450 reserves cavities for the first drain electrode 442 andthe second drain electrode 443 to penetrate therethrough; the cavitiesmay closely surround the first drain electrode 442 and the second drainelectrode 443. In one embodiment, the first drain electrode 442, thesecond drain electrode 443 and the dielectric layer 441 are a partialstructure of the TFT structure 440, but the invention is notparticularly limited herein. A material of the organic film 450 includesone or more of polyethylene, polypropylene, polystyrene, polylacticacid, polyethylene terephthalate, polyimide and polyester; a thicknessof the organic film 450 is 0.5-20 μm. The organic film 450 and thesecond polyimide layer 430 are all organic polymers, and therefore, theorganic film 450 and the second polyimide layer 430 can be formed moreclosely. By adding the organic film 450 on the surface of the TFTstructure 440 in a driver display and connecting the organic film 450 onthe second polyimide layer 430, the folding display of the OLED displaypanel can be greatly enhanced, and the folding resistance of the panelcan be improved.

Another embodiment of the present invention provides a flexible OLEDdisplay panel 500, which includes, as shown in FIG. 5, a first polyimidelayer 510, a barrier layer 520 and a second polyimide layer 530 that aresequentially stacked and an oxygen barrier layer 550, a TFT structure540, an organic film 560 and an OLED structure (not shown in FIG. 5)that are sequentially disposed on second polyimide layer 530. The oxygenbarrier layer 550 is disposed between the second polyimide layer 530 andthe TFT structure 540 and adheres together with a buffer layer 541 ofthe TFT structure 540; a material of the oxygen barrier layer 550includes at least one of silicon dioxide and silicon nitride; athickness of the oxygen barrier layer 550 is 0.1-1.5 μm. The organicfilm 560 is disposed between the TFT structure 540 and the OLEDstructure, and the organic film 560 simultaneously covers a side edge ofthe TFT structure 540 that is near a terminal of a non-display area andpartially covers the second polyimide layer 530; the organic film 560 isstacked on a dielectric layer 542, and simultaneously the organic film560 and the TFT structure 540 are all stacked on the second polyimidelayer 530; a material of the organic film 450 includes one or more ofpolyethylene, polypropylene, polystyrene, polylactic acid, polyethyleneterephthalate, polyimide and polyester; a thickness of the organic film450 is 0.5-20 μm. The flexible OLED display panel 500 of the embodimentsimultaneously includes the oxygen barrier layer 550 and the organicfilm 560 and not only has superior water and oxygen blocking functionand longer luminescent lifespan but also has folding resistance.

Furthermore, an embodiment of the present invention further provides aflexible OLED display panel 300, which further includes an organic film360; the organic film 360 is stacked between the TFT structure 350 andthe OLED structure 370 and extends to the upper surface of the secondpolyimide layer 330, and the organic film 360 covers a side face of aterminal of the TFT structure 350, and a material of the organic film360 includes one or more of polyethylene, polypropylene, polystyrene,polylactic acid, polyethylene terephthalate and polyester.

As shown in FIG. 6, the present invention further provides amanufacturing method of a flexible OLED display panel, which includesthe following steps:

S10, providing rigid substrate;

S20, sequentially manufacturing a first polyimide layer, a barrierlayer, a second polyimide layer, a TFT structure and an OLED structureon the rigid substrate;

S30, applying a laser lift-off process to separate the rigid substrateand the first polyimide layer, so as to obtain a flexible OLED displaypanel.

In one embodiment of the present invention, in S10, the rigid substratemay be a glass substrate, a wafer, a metal thin film or a rigid thinfilm. The rigid substrate is required to have a higher lasertransmittance for facilitating the subsequent light lift-off process tobe performed smoothly. Certainly, in order to have batter adherence ofthe rigid substrate and subsequent light-to-heat conversion layer andflexible substrate layer, a surface treatment may be performed on therigid substrate for improving the surface energy of the rigid substrate.In one embodiment of the present invention, the surface treatmentincludes: cleaning the surface of the rigid substrate; then using noblegas such as nitrogen and argon to perform a plasma treatment on thecleaned surface of the rigid substrate. By performing the abovetreatment, the surface energy of the rigid substrate can be improved,and the binding force between the first polyimide layer and the rigidsubstrate is enhanced, so as to prevent the first polyimide layer andthe rigid substrate from stripping or falling during the subsequentprocesses.

In one embodiment of the present invention, in S20, a material of thefirst polyimide layer and the second polyimide layer is polyimide resinor modified polyimide resin; a thickness ranges of the first polyimidelayer and the second polyimide layer are all 3-20 μm, but specificthicknesses of the first polyimide layer and the second polyimide layermay be different.

Specifically, the step of manufacturing the first polyimide layer on therigid substrate includes:

respectively forming vapor of monomers from an aromatic tetracarboxylicdianhydride monomer and a diamine monomer and then mixing the vapor ofmonomers, and depositing the mixed vapor on the rigid substrate; thenperforming a polyimidization treatment on the dianhydride monomer andthe diamine monomer that are deposited on the rigid substrate, so as toobtain a PI layer. In one embodiment, during the evaporation process ofthe aromatic tetracarboxylic dianhydride monomer and the diaminemonomer, the evaporation temperature of the aromatic tetracarboxylicdianhydride monomer is 150-180° C., and the evaporation temperature ofthe diamine monomer is 60-160° C. The polyimidization treatment may beperformed in an infrared stove, and the treatment process adopts heatingto 320-385° C. from the room temperature by the rate of 0.5-3° C./minunder the protection of nitrogen gas and then keeping 1-3 hours; andthen naturally cooling down to the room temperature, so as to obtain thePI layer.

In one embodiment of the present invention, in S20, the barrier layer isarranged between the first polyimide layer and the second polyimidelayer, and a material of the barrier layer 20 includes one or two ofsilicon dioxide and silicon nitride; a thickness of the barrier layer 20is 0.1-2.0 μm, and particularly, may be 0.2 μm, 0.8 μm, 1 μm or 1.5 μm.The barrier layer may further include silicon dioxide layers and siliconnitride layers that are alternately stacked. The manufacturing step ofthe barrier layer on the first polyimide layer is: placing a thin filmlayer that includes one or two of silicon dioxide and silicon nitride onthe first polyimide layer by performing a plasma enhanced chemical vapordeposition (PECVD) process or a magnetron sputtering process, ormanufacture various types of thin films formed of alternating layers ofsilicon dioxide and silicon nitride, so as to obtain the barrier layer.

Preferably, S20 further includes manufacturing an oxygen barrier layerbetween the second polyimide layer and the OLED structure and/ormanufacturing an organic film between the TFT structure and the OLEDstructure; a material of the oxygen barrier layer includes at least oneof silicon dioxide and silicon nitride, the organic film simultaneouslycovers a side edge of the TFT structure that is near to a terminal ofthe non-display area and partially covers the second polyimide layer,and a material of the organic film includes one or more of polyethylene,polypropylene, polystyrene, polylactic acid, polyethylene terephthalateand polyester.

In one embodiment of the present invention, in S20, the manufacturingmethods of the second polyimide layer and the first polyimide layer arethe same; the TFT structure and the OLED structure may be manufacturedin accordance with a normal process in the field, and the presentinvention does not make particular limitations.

In one embodiment of the present invention, in S30, the specific step ofapplying a laser lift-off process to separate the rigid substrate andthe first polyimide layer is: illuminating a 343 nm laser onto the rigidsubstrate, such that a portion of the first polyimide layer near to therigid substrate is melted, thereby realizing the first polyimide layerand the rigid substrate through a laser lift-off process, so as toobtain a complete first polyimide layer.

It is noted that those skilled in the art can also make changes andmodifications to the aforementioned embodiments according to theaforementioned disclosures and descriptions of the specification.Accordingly, the present invention is not limited to the above disclosedand described specific embodiments, and a number of equivalentmodifications and changes should also be within the claim scope of thepresent invention. In addition, although some specific terms are used inthe specification, these specific terms are merely for convenience ofexplanation but do not make any limitations to the present invention.

What is claimed is:
 1. A flexible organic light-emitting diode (OLED)display panel, comprising a first polyimide layer, a barrier layer and asecond polyimide layer that are sequentially stacked and a thin filmtransistor (TFT) structure and an OLED structure that are sequentiallystacked on the second polyimide layer, an oxygen barrier layer disposedbetween the second polyimide layer and the TFT structure, wherein thebarrier layer comprises a single-layered silicon dioxide layer or asingle-layered silicon nitride layer, or comprises alternately stackedsilicon dioxide layers and silicon nitride layers, and wherein the TFTstructure comprises a first drain electrode and a second drainelectrode; an organic film disposed between the TFT structure and theOLED structure, wherein the organic film reserves cavities for the firstdrain electrode and the second drain electrode to penetratetherethrough; the cavities surround the first drain electrode and thesecond drain electrode, and wherein the organic film covers a side edgeof the TFT structure and in contact with the second polyimide layer andthe oxygen barrier layer.
 2. The flexible OLED display panel accordingto claim 1, wherein a thickness of the barrier layer is 0.1-2.0 μm. 3.The flexible OLED display panel according to claim 1, wherein a materialof the oxygen barrier layer comprises at least one of silicon dioxideand silicon nitride.
 4. The flexible OLED display panel according toclaim 1, wherein a material of the organic film comprises one or more ofpolyethylene, polypropylene, polystyrene, polylactic acid, polyethyleneterephthalate, polyimide and polyester.
 5. The flexible OLED displaypanel according to claim 1, wherein a material of each of the firstpolyimide layer and the second polyimide layer is polyimide resin ormodified polyimide resin.
 6. The flexible OLED display panel accordingto claim 1, wherein a thickness of each of the first polyimide layer andthe second polyimide layer is 3-20 μm.
 7. The flexible OLED displaypanel according to claim 3, wherein a material of the organic filmcomprises one or more of polyethylene, polypropylene, polystyrene,polylactic acid, polyethylene terephthalate, polyimide and polyester.